Wnt signaling drives hair follicle regeneration in wounds by attenuating mechanotransduction in the epidermis

Summary: Abstract Body: Most wounds heal as scars, which lack hair follicles that serve as crucial reservoirs of stem cells on the skin. However, in the wound-induced hair neogenesis(WIHN) model of skin regeneration, optimal tissue rigidity of the wound allows for hair follicle regeneration. Wnt signaling is needed for WIHN, but whether Wnt serves a potential mechanoregulatory role that allows for regeneration to occur is unknown. Here, we show that Wnt regulates mechanosensitivity at cellular and tissue levels to drive WIHN in mice. Using atomic force microscopy, we found that Wnt attenuates the substrate rigidity response in epidermal keratinocytes but not dermal fibroblasts of healed wounds. Super-resolution microscopy and nanoneedle probing of live human keratinocytes revealed that Wnt-induced chromatin remodeling lowers nuclear rigidity by ~90%, while preserving nucleo-cytoskeletal mechanical coupling—a vital mechanism for relaying mechanosensitive information between the cytoplasm and the nucleus. Our mechanistic studies showed via traction force microscopy and live-cell imaging that Wnt drives massive reorganization of the actin network and recruits adherens junctions(AJs) to form a mechanical syncytium—a cohesive multicellular unit with superb capacity for force coordination. Since AJs anchor actin filaments at cell-cell junctions, the actin network in cells with amplified Wnt exhibited a “hollowed-out” appearance—sparse in the center and rich in the periphery(cell-cell junctions), where junctional actin filaments became highly organized. Overall, our findings revealed Wnt signaling’s novel mechanoregulatory function that manipulates the mechanotransduction machinery to drive regeneration. Allen S. Oak¹, Amrit Bagchi², Matthew J. Brukman³, Joshua Toth², T. Jamie Ford³, Ying Zheng¹, Arben Nace¹, Ruifeng Yang¹, James Hayden⁴, Gordon Ruthel⁵, Anisa Ray¹, Elaine Kim¹, Vivek Shenoy², George Cotsarelis¹ 1. Dermatology, University of Pennsylvania, Philadelphia, PA, United States. 2. Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, United States. 3. Singh Center for Nanotechnology, University of Pennsylvania, Philadelphia, PA, United States. 4. Wistar Institute, Philadelphia, PA, United States. 5. University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, United States. Stem Cell Biology, Tissue Regeneration and Wound Healing